ANTAGONISM 137 



The ordinates represent the growth of roots in the 

 various mixtures. 



The antagonism at any point is the total growth 

 minus the growth which would have taken place if no 

 antagonism existed. This antagonism is best expressed 

 as percentage of the growth which would have taken place 

 in the absence of antagonism. Hence the antagonism at 

 the point G is expressed as 100 (GD — FG) -— FG. 



The figure shows in a diagrammatic way the effect of 

 dilution on the form of an antagonism curve. The lowest 

 curve CDE shows the effect on growth of various mix- 

 tures of two equally toxic solutions A 0.1 M -{- B 0.12 M. 

 The next curve shows the form of the antagonism curve 

 when all of these mixtures were diluted by the addition 

 of an equal volume of water {A 0.05 M + B 0.06 M). The 

 next curve was produced by growing plants in mixtures of 

 A 0.0025 M + B 0.03 M. The topmost curve was obtained 

 with mixtures of A 0.001 M + B 0.0012 M. 



The pairs of pure solutions were in each case equally 

 toxic, as is shown by the fact that the two ordinates at 

 the ends of each curve are equal in height. 



It will be observed that as the solutions become more 

 dilute, the antagonism curve becomes flatter, and it is 

 evident that at still greater dilutions it must tend to 

 become a horizontal straight line. 



In order to give a complete description of the changes 

 in the antagonism curve as dilution increases, it is neces- 

 sary to construct a solid model. This might have as its 

 base a triangular diagram as previously described. The 

 apices of the triangle would in that case represent, A, B, 

 and H2O. 



It is more suitable for our present purpose to employ 

 a square as the base and to represent the composition of 



